San Diego restaurant owners say they are feeling even more pressure in a tough economy now that the Supreme Court has upheld the Affordable Care Act and employers will have to start providing health insurance to workers.

Starting in 2014, companies with at least 50 employees must provide affordable health insurance or pay a penalty of $2,000 per worker, after the first 30 employees.

In San Diego County, about 4,250 companies fall into that category of employing at least 50 people, and, according to UCLA’s California Health Interview Survey, more than 100,000 people working at those businesses don’t have health insurance.

More than half the businesses are restaurants, industry figures show. And because profit margins are often low, restaurants typically don’t provide health insurance to employees.

The federal mandate aims to change that.

“The restaurant industry is really affected by this,” said owner James Brennan.

Since 2009, Brennan and partner Brian Malarkey have created 600 jobs among their five trendy restaurants, a nightclub and catering company in San Diego.

“In a business like mine, where profits can be razor thin, what this is going to end up doing is passing that cost on to the consumer,” Brennan said. “Whether that means an increase in the price of the steak or the price of the beer you order, this is going to come out of consumers’ pockets.”

The California Restaurant Association has long opposed the mandate, said Chief Executive Jot Condie.

“To put this kind of cost on our industry will have a dire impact,” he said, noting that California has 10,000 fewer restaurants now than before the recession.

“These are not hugely profitable businesses. For every dollar a restaurant takes in, it usually keeps three or four pennies.”

Condie said “the worst-case scenario” is that restaurant owners will opt to pay the $2,000 penalty and tell employees to buy insurance on the California Health Benefit Exchange.

Insurance exchanges, also required under the federal law, are to open in every state in 2014 as a place for individuals and for businesses with fewer than 100 workers to comparison shop and buy a health plan at group rates. Federal subsidies will be available to many people to help with premium costs.

Even before the Affordable Care Act was signed into law in 2010, business groups predicted that employers who don’t provide insurance will balk at the mandate, and those that do provide insurance now may decide it’s cheaper and simpler to just pay the penalty and tell workers to buy their own policies on the exchange.

Health care advocate and attorney Gregory Knoll said he believes that won’t happen, in part because businesses will benefit from more stable premium costs because the Affordable Care Act expands the pool of healthy policyholders.

“Most employers simply want to know what they’re going to pay, because then they can plan for it,” said Knoll, who is executive director of the Legal Aid Society of San Diego and its Consumer Center for Health Education and Advocacy.

“But most employers I’ve talked to want to find a way to do this for their employees because it promotes a healthier workforce and a healthier work environment,” he said. “It’s not just about the bottom line. It’s about how you feel about your employees and their families.”

Despite predictions that employers will opt to pay the penalty and not insure their workers, that hasn’t been the pattern in Massachusetts, the nation’s sole testing ground for health care reform, said Christine Eibner, an economist with the Rand Corp. think tank.

“A lot of employers say they will drop coverage,” said Eibner, an expert on the effect of health care reform on businesses. “But the one piece of evidence is the state of Massachusetts, where there actually was a slight increase in coverage.”

Her research found that after the Massachusetts mandate started in 2007, workers often pressured employers to provide coverage. As in Massachusetts law, the Affordable Care Act penalizes both the employer and the employee if the worker doesn’t have coverage.

Companies could opt to pay their penalty and possibly even reimburse employees for theirs, and the employees could buy insurance at the state exchange.

While that might seem like a deal for the boss, workers saw it differently, Eibner said. When workers pay insurance premiums on employer-based policies, it’s done using pre-income tax dollars — while buying on the exchange is a post-tax expenditure.

“So it’s not as good a deal for employees,” she said.

Eibner noted that companies with mostly low-wage workers — like restaurants — are more likely to drop their health plans. And it remains to be seen whether the dynamics in Massachusetts apply in an era of high unemployment, when employers have the advantage, Eibner said.

“I think it depends on what the economy looks like in 2014,” she said. “But that is an uncertainty.”

California has its own test case. Since 2007, businesses with at least 20 workers have paid for their uninsured employees to participate in the “Healthy San Francisco” medical access program. The employer fee is used either to pay for an employee’s medical care at city clinics, or to fund a medical expenses reimbursement account for the employee. Businesses with 20 to 99 employees pay a fee of $1.46 per hour per worker; for businesses with 100-plus employees, the fee is $2.20 per hour per worker.

“Restaurants here in the city have added a surcharge onto menus that can range from $1 per person to 4 percent per meal,” Black said. Truck rental companies, nail salons and others also have added surcharges to their bills, he said.

Using a surcharge rather than just raising prices serves two purposes, Black said. First, it notifies customers where their money is going. Second, the surcharge isn’t calculated into the rent for businesses with a lease based on gross revenue.

Black said the fee has discouraged businesses from expanding.

“What we’ve seen are these false ceilings in hiring,” he said. “People don’t want to go beyond 19 employees, or beyond 99 employees.”

That’s the kind of decision Brennan expects to start making as he and his partner continue opening restaurants, he said.

Beyond raising prices to pay for employee health benefits, Brennan said, all of his new restaurants may be smaller, with fewer than 50 employees.

Each of his restaurants now is about 8,000 square feet, which requires about 75 employees. That was the original plan when he began scouting for a location to open a restaurant in Los Angeles. But after the Supreme Court ruling last Thursday, Brennan said he called up his leasing agent to say he wanted to look at smaller properties over the weekend.

“Instead of looking for that 70- to 75-employee size, I’m looking for square footage for 49 employees,” he said. “This is not the way I should be forced into thinking.”

Brennan said that if he had limited his staffing starting in 2009, he’d be employing 400 people today instead of 600.

“Some of these people who are applauding (the employer insurance mandate) need to be asked, do they want to be guaranteed insurance or do they want a job? Because that’s the choice,” he said. “This is real.”